I don't think proponents of catharsis are claiming that screaming at a tree if going to instantly make you calmer, it's that later that day you might feel better.
Also, participants were instructed to focus their anger on the perpetrator of the criticism, whereas it's probably healthier and more effective to simply focus on releasing your aggression.
Or, a combo study would be interesting where participants are instructed to hit a punching bag and then try to empathize with themselves or others, vs. only trying to empathize.
Anyway, it's an interesting study, but I'm not sure I'd rule out catharsis just yet.